coming from a guy who owns a Cadillac, i wouldnt buy another one when its out of its warranty
the XLR have the northstar engine in them as far as i know, with such high mileage, i would turn my head and walk away

The XLR shares the same 4.6L engine as Sam and I'* Bonneville GXP. If they have never been run hot, (ever) alot make it over the 200K mark. But they are prone to head warpage, blown head gaskets, stripped head bolts. Things to consider if you don't know prior history of one. They are also prone to oil and water crossover leaks regardless. At 100k you can expect suspension parts and sensors to begin wearing out as well. The 4.6 is a throwaway engine. When its done, it'* done. So alot depends on how the car was kept up. You could be throwing alot more the the purchase price into one.